Ronald Breslow (Columbia University), a former President of the American Chemical Society, has made significant contributions to fundamental chemistry, for example, in the study of antiaromatic compounds and also bioorganic chemistry. Currently, he is trying to prepare artificial enzymes that can imitate the function of natural enzymes. Breslow is involved in the synthesis of mimics of antibodies or of biological receptor sites, for example, for modulating the activity of peptide hormones. He also has a long-standing program to develop novel compounds that can induce cells to differentiate. These have important potential in cancer treatment and are now in human trials.